I'm searching for this too and tried to workaround it a little bit.
I think that every object in your db has to be a unique id (or just iterate through). Then in your code at node
object you could write something like this:
var node = svg.selectAll(".node")
.data(graph.nodes)
.attr("r", function(d){
if (d.value === myUniqueId){
return 3;
} else {
return 10;
}
})
here the "r"
is for the radious.The value
is a name in my db (it can be anything you want). There you can change the nodes sizes.
I know it is not a clean code but I'm just a newbie.
Hope it helps!